This invention relates to contact lenses, and more particularly to a contact lens of the rigid type which exhibits wettable characteristics.
Contact lenses of the hard type are characterized generally by a relatively rigid structure. They have good optical properties and may be provided in a wide range of precise optical specifications. However, heretofore they have presented a number of problems and disadvantages to the wearer, primarily because of their hydrophobic surface characteristics. Thus, because they do not wet adequately with tears, they may cause eyelid irritation, eye abrasion, edema, spectacle blur and corneal distortions.
Because of the foregoing problems, recent efforts have been directed to the development of soft contact lenses. Such lenses are hydrophilic in character and thus are readily wet by tears and hence less irritating to the eyes. In fact, the degree of comfort is such that they often are worn too long, resulting in corneal edema and other adverse effects. Their optical properties are rather poor, however, varying unpredictably with variations in such factors as hydration during storage and use, thereby contributing adversely to reduced visual acuity. Also, they are usable only in the low ranges of optical corrections. Moreover, verification of lens specification is extremely difficult, whereby to seriously reduce the possibility of successful fitting and reproducibility of physical and optical parameters. Still further, they are quite vulnerable to contamination by fungi and bacteria, to such extent that unless maintained sterile during storage and use, serious eye infections may result.